To enable piloting of an aircraft, the aircraft cockpit is typically provided with various flight controls (e.g., one or more flight yokes) and instrumentation, which often includes a considerable number of back-lit display systems. A representative aircraft display system comprises a display head assembly, which is mounted on a chassis. The display head assembly typically comprises a bezel and a display head, which includes a housing and display screen (e.g., a liquid crystal display) mounted within the housing. The bezel is coupled to the face of the display head and may include various controls for operating the display (e.g., display brightness, gain, contrast, etc.).
Aircraft display systems of the type described are known to emit stray light. Stray light emissions must often be managed to reduce glare and to minimize interference with light-sensitive night vision systems that may be deployed on the aircraft. Consequently, aircraft regulations may require that the quantity of light reaching a particular area of the cockpit (e.g., the region occupied by the pilot or co-pilot) does not exceed a predetermined threshold. For this reason, light filters may be employed to reduce the emission of stray light. Light filters may reduce the quantity of stray light reaching a particular area of the cockpit by, for example, only permitting light to pass through the filter at angles falling within a predetermined range of viewing angles. Such light filters are most effective when they are placed adjacent the display screen. As used herein, the term light filter includes filter elements that may block various spectra of electromagnetic radiation, including, but not necessarily limited to, electromagnetic radiation falling within the visible, ultraviolet, and infrared spectrums. For example, visible light filters may block green, blue, and red wavelengths of light to accommodate night vision optics. Other filters may include clear plastic with etched target markings or screen print target markings for different test procedures and photometer readings. Certain light filters (e.g., black plastic, mirror, and wood filters) may also be employed to completely block out light or to shield the display from sun or excessive heat. Furthermore, a metal shield filter may be employed to prevent display from being physically damaged (e.g., by pilot trying to enter cockpit).
Light filters are conventionally mounted to a display head assembly by attaching the light filter directly to the display screen with, for example, a Velcro fastener, double-sided tape, lace tape, or the like. Attaching the light filter to the display screen in this manner is relatively cumbersome. In addition, such attachment means may be somewhat unreliable and may result in visual obstruction of the display screen. Furthermore, these techniques do not allow the light filter to be easily replaced or reoriented (e.g., to change the angles at which the filter blocks stray light).
Considering the foregoing, it should be appreciated that it would be desirable to provide a filter frame capable of being retrofitted to an existing display head assembly, which may reliably secure a light filter in front of the assembly's display screen and which readily permits manual replacement or reorientation of the light filter. It would also be desirable to provide a display head assembly including a display head and bezel that cooperate to form a filter frame suitable for removably holding a light filter adjacent the display screen. Other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.